Extracting hemicellulose prior to pulping is a proposed method of creating new feedstocks in an integrated forest products bio-refinery.  Hemicellulose can be extracted without causing significant yield loss to the more valuable pulp product if alkaline chemicals are used to maintain the final extract liquor at near-neutral pH conditions.  Acetyl groups liberated from the hemicellulose polymer during extraction are neutralized by the added alkali, and represent a valuable co-product.  The aqueous extract contains xylo-oligosaccharides which can be hydrolyzed and utilized by pentose fermenting organisms to produce ethanol or other value-added products.

Mixed southern hardwood chips were extracted with either carbonate or green liquor, a pulping intermediate containing NaOH, Na₂S and Na₂CO₃, at 0, 2, 4 and 6% TTA (total titratable alkali) for each of the two chemicals. The extractions were also performed for each chemical charge condition at low, medium and high H-factors (a kinetic model expressing cooking time and temperature as a single variable) to determine the effect of extraction severity on pulp yield and composition of the extracted liquor.  The severity of hemicellulose extraction in terms of time and alkaline charge determines the concentration of acetic acid and monosaccharides available for downstream processing, the pulp yield attainable for extracted fiber, and the accumulation of degradation products such as organic acids and furans.  Complete compositional data and the corresponding pulp yield effects will be presented for each of the conditions tested.